POS0306 INVOLVEMENT OF CENTRAL SENSITIZATION IN PATIENTS WITH AXIAL SPONDYLOARTHRITIS; A BIOPSYCHOSOCIAL APPROACH
Authors: Y. Van der Kraan, D. Paap, H. Timmerman, F. Wink, S. Arends, M. Reneman, A. Spoorenberg
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Chronic (inflammatory) back pain is a key symptom of axial spondylarthritis (axSpA) and still present in a large proportion of patients on long-term biological treatment. This pain may not only be of inflammatory origin, but also due to altered pain processing of the central nervous system such as central sensitization (CS). Biological, psychological and social factors contribute to the development and maintenance of CS. A high score on the Central Sensitization Inventory (CSI), is associated with disease activity in axSpA.[1] In absence of a gold standard, Quantitative Sensory Testing (QST) is currently understood as an optimal indirect assessment of altered somatosensory function. However, QST is not always feasible in clinical practice, and CSI could serve as an alternative. <h3>Objectives</h3> To explore: 1) to what extent altered somatosensory function related to CS is present in patients with axSpA; 2) associations with QST and psychosocial factors related to CS. <h3>Methods</h3> Consecutive outpatients from the Groningen Leeuwarden axSpA cohort, fulfilling the ASAS classification criteria, were included. Participants underwent QST according to a standardized protocol, including assessment of Pain Pressure Threshold (PPT) at 11 sites, Temporal Summation (TS) at 3 sites and Conditioned Pain Modulation (CPM). Widespread low PPTs, high TS (both pain facilitation) and positive CPM (impaired pain inhibition) are indicators of CS. Participants also filled out the CSI, illness perception (IPQ-R), pain catastrophizing (PCS), fatigue (MFIS), anxiety and depression (HADS), coping (CORS) and physical activity (mSQUASH). Analyses were stratified for CSI cut-off value ≥40 indicating probable CS. Univariable and multivariable linear regression analyses were used to investigate the association of CSI, the questionnaires, QST, and patient and disease related assessments. <h3>Results</h3> 201 patients were included, median age was 50 years [IQR 38-58], 63% were male, 64% were classified as radiographic axSpA, 79% were HLA-B27+, median symptom duration was 12 years [IQR 5-24], mean ASDAS<sub>CRP</sub> was 2.1 ± 1.0. In total, 40% patients scored ≥40 on the CSI. In these patients PPTs at all sites except the m. trapezius left were significantly lower and TS significantly higher at the non-painful and painful area compared to patients with CSI scores &lt; 40 (Table 1). No significant differences in TS at the non-dominant forearm and CPM were found. In univariable linear regression, sex, ASDAS, BASFI, PPT scores, PCS, IPQ-R identity, IPQ-R emotional representations, IPQ-R consequences, MFIS, HADS anxiety, CORS pain decreasing activities and mSQUASH were all significantly associated with the CSI. In the multivariable regression model, 5 variables (MFIS, IPQ-R Identity, sex, HADS anxiety, and PCS) were independently associated with the CSI. Explained variance of this model was 78%. Excluding the CSI questions with potential overlap with symptoms related to axSpA resulted in a comparable model. <h3>Conclusion</h3> This large study including QST confirms that altered somatosensory function related to CS is present in a subgroup of patients with axSpA. In addition, the CSI strongly reflect psychosocial factors related to CS. These results addresses the importance of the multifactorial biopsychosocial perspective of pain within the management of axSpA. <h3>Reference</h3> [1]Kieskamp SC et al. Rheumatology (Oxford) 2021 <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> Yvonne van der Kraan: None declared, Davy Paap: None declared, Hans Timmerman: None declared, Freke Wink: None declared, Suzanne Arends: None declared, Michiel Reneman: None declared, Anneke Spoorenberg Grant/research support from: ReumaNederland Grant.